Increase storage capacity by striping data accross objects in sync storage

[psidex]

Currently we can only store the settings as a compressed object that is under 8192 bytes in size.

This is because we are storing it in a single sync storage entry, but browsers allow for 512 entries, which are allowed to total 102400 bytes in size. Splitting the settings data up into multiple objects and striping it across these entries will allow us to use that whole allowance.

This library may be of use - https://github.com/dtuit/chrome-storage-largeSync.